Units of time

1000 milliseconds = 1 second
60 seconds = 1 minute
60 minutes = 1 hour
24 hours = 1 day
7 days = 1 week
28-31 days = 1 month
365 or 366 days = 1 year
12 months = 1 year
10 years = 1 decade
100 years = 1 century
1000 years = 1 millennium

See also:
Telling the time